2 Answers
2

There certainly is a common error people seem to be making based on what I have read in this article:

Improper sequencing. Front squats are deceiving because while it's a primarily knee-dominant movement pattern, you still want to initiate the movement from the hips first and push your butt back before breaking from the knees.

It's an almost simultaneous hip/knee break, but it's important that it happens in that order: first back, and then down. Breaking from the knees first will create excessive sheer forces on the knee – not good.

To help ingrain the idea of sitting back, it may be helpful to put a box behind you for a little while. This isn't your typical box squat where you try to keep a vertical tibia and pause on the box. Your form should mirror a regular front squat and the box just there as a reminder to initiate the movement from the hips.

This was the mistake I was making. Due to the fact that the front squat is primary a knee dominant movement I was initiating from the knees and not the hips.

The next time you're due to front squat, be mindful of this and make sure to initiate out of the hips just like you would in a back squat.

good answer. I want to add, that your torso is more upright while front squatting, due to your hip movement isn't as long as doing a low bar back squat. Otherwise the bar would have been fallen of your shoulers. Therefore you'll have to shift your knees a little bit more over your toes which effects your knees / quads more.
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mchlfchrSep 26 '13 at 7:33

Odds are your knees are not tracking out far enough. You should be spreading your knees as wide as possible throughout the movement. A perfect front squat is performed with the toes pointing straight forward. If you don't have the flexibility to do that, it's okay to point your toes out a bit. The further out your toes point, the worse it is on your knees. A good range of motion test is to try doing a full squat (butt to ankles) with your feet together without falling backwards. You should also be able to reach the same depth with your feet at shoulder width.

You should also be concerned about thoracic extension. Hopefully you are performing this exercise with a clean grip rather than a folded-arm grip. A zombie squat is also acceptable if you don't have the mobility to use a clean grip. This will help force your pelvis to remain level throughout the movement because you won't be tempted to compromise hip position by leaning forward.